U.S. patent application number 12/540645 was filed with the patent office on 2010-03-18 for system and method for system switch and handover between wireless communication systems.
This patent application is currently assigned to Industrial Technology Research Institute. Invention is credited to Yung-Han Chen, Chi-Fang Li, Fang-Ching Ren.
Application Number | 20100069073 12/540645 |
Document ID | / |
Family ID | 41467254 |
Filed Date | 2010-03-18 |
United States Patent
Application |
20100069073 |
Kind Code |
A1 |
Chen; Yung-Han ; et
al. |
March 18, 2010 |
SYSTEM AND METHOD FOR SYSTEM SWITCH AND HANDOVER BETWEEN WIRELESS
COMMUNICATION SYSTEMS
Abstract
A method of a base station for wireless communication includes
providing a first zone and a second zone for wireless
communication; operating the first zone using a first operation
mode; and operating the second zone using a second operation mode.
The method also includes communicating with a mobile station in the
first zone using the first operation mode; determining whether the
mobile station is capable of operating using both the first
operation mode and the second operation mode; and performing, if
the mobile station is determined to be capable of operating using
both the first and second operating modes, a zone switch procedure
to switch the mobile station from the first zone using the first
operation mode to the second zone using the second operation
mode.
Inventors: |
Chen; Yung-Han; (Hsinchu
City, TW) ; Ren; Fang-Ching; (Hsinchu City, TW)
; Li; Chi-Fang; (Tongsiao Township, TW) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER;LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Assignee: |
Industrial Technology Research
Institute
|
Family ID: |
41467254 |
Appl. No.: |
12/540645 |
Filed: |
August 13, 2009 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61096754 |
Sep 12, 2008 |
|
|
|
Current U.S.
Class: |
455/437 ;
455/436 |
Current CPC
Class: |
H04W 88/10 20130101;
H04W 36/14 20130101 |
Class at
Publication: |
455/437 ;
455/436 |
International
Class: |
H04W 36/00 20090101
H04W036/00 |
Claims
1. A method of a base station for wireless communication,
comprising: providing a first zone and a second zone for wireless
communication; operating the first zone using a first operation
mode; operating the second zone using a second operation mode;
communicating with a mobile station in the first zone using the
first operation mode; determining whether the mobile station is
capable of operating using both the first operation mode and the
second operation mode; and performing, if the mobile station is
determined to be capable of operating using both the first and
second operating modes, a zone switch procedure to switch the
mobile station from the first zone using the first operation mode
to the second zone using the second operation mode.
2. The method according to claim 1, wherein the first operation
mode is one of a legacy operation mode and an advanced operation
mode; and the second operation mode is the other one of the legacy
operation mode and the advanced operation mode.
3. The method according to claim 1, wherein performing the zone
switch procedure includes: performing the zone switch procedure
using a make-before-break method.
4. The method according to claim 1, wherein performing the zone
switch procedure includes: performing the zone switch procedure
using a break-before-make method.
5. A method of a mobile station capable of communicating in a first
operation mode and a second operation mode, comprising: operating
in the first operation mode for communicating with a first zone of
a base station; establishing a communication link with the base
station using the first operation mode; determining that the base
station is capable of operating in both the first operation mode
and the second operation mode; performing a zone switch procedure
to switch the mobile station from the first zone using the first
operation mode to a second zone using the second operation mode;
and operating in the second operation mode for communicating with
the second zone of the base station.
6. The method according to claim 5, wherein the first operation
mode is one of a legacy operation mode and an advanced operation
mode; and the second operation mode is the other one of the legacy
operation mode and the advanced operation mode.
7. The method according to claim 6, wherein the mobile station
determines that the base station is capable of operating in both
the first operation mode and the second operation mode based on a
zone indicator from the base station.
8. The method according to claim 5, wherein performing the zone
switch procedure includes: performing the zone switch procedure
using a make-before-break method.
9. The method according to claim 5, wherein performing the zone
switch procedure includes: performing the zone switch procedure
using a break-before-make method.
10. A method of a communication network for wireless communication,
comprising: providing a first base station capable of operating in
a first operation mode; providing a second base station capable of
providing one or more zones and operating in at least a second
operation mode; providing at least one mobile station capable of
operating in the first operation mode and the second operation
mode; communicating, by the mobile station, with one of the first
base station and the second base station; and performing a handover
procedure to hand over the mobile station between the first base
station and the second base station.
11. The method according to claim 10, wherein the first operation
mode is a legacy operation mode; and the second operation mode is
an advanced operation mode.
12. The method according to claim 11, wherein the one or more zones
include a first zone operating in the first operation mode and a
second zone operating in the second operation mode and performing
the handover procedure includes: obtaining, by the mobile station,
information about the first zone of the second base station from
the first base station; performing the handover procedure from the
first base station to the first zone of the second base station;
obtaining, by the mobile station, information about the second zone
of the second base station from the first zone of the second base
station; and performing a zone switch from the first zone of the
second base station to the second zone of the second base
station.
13. The method according to claim 11, wherein performing the
handover procedure includes: obtaining, by the mobile station,
information about a selected zone of the one or more zones of the
second base station, the selected zone operating in the second
operation mode, from the first base station; and performing the
handover procedure from the first base station to the zone of the
second base station.
14. The method according to claim 11, wherein the one or more zones
include a first zone operating in the first operation mode and a
second zone operating in the second operation mode and performing
the handover procedure includes: obtaining, by the mobile station,
information about the first zone of the second base station from
the first base station; starting the handover procedure from the
first base station to the first zone of the second base station;
receiving, by the mobile station, information about the second zone
of the second base station from the first zone of the second base
station before the handover procedure is completed; and completing
the handover procedure to hand over the mobile station from the
first base station to the second zone of the second base
station.
15. The method according to claim 11, wherein performing the
handover procedure includes: obtaining, by the mobile station,
information about the first base station from the second base
station; and performing the handover procedure from a selected zone
of the one or more zones of the second base station to the first
base station, the selected zone operating in the second operation
mode.
16. The method according to claim 11, wherein the one or more zones
include a first zone operating in the first operation mode and a
second zone operating in the second operation mode and wherein
performing the handover procedure includes: obtaining, by the
mobile station, information about the first base station from the
second base station; performing the handover procedure from the
second zone of the second base station to the first base station;
before performing the handover procedure, performing a zone switch
from the second zone of the second base station to the first zone
of the second base station.
17. A base station for wireless communication, comprising: one or
more antennas; a transceiver coupled to the one or more antennas
for receiving and transmitting communication data from and to
mobile stations; and a processor configured to: provide a first
zone and a second zone for wireless communication; operate the
first zone using a first operation mode; operate the second zone
using a second operation mode; communicate with a mobile station in
the first zone using the first operation mode; determine whether
the mobile station is capable of operating using both the first
operation mode and the second operation mode; and perform a zone
switch procedure to switch the mobile station from the first zone
using the first operation mode to the second zone using the second
operation mode, if the mobile station is determined to be capable
of operating using both the first operation mode and the second
operation mode.
18. The base station according to claim 17, wherein the first
operation mode is one of a legacy operation mode and an advanced
operation mode; and the second operation mode is the other one of
the legacy operation mode and the advanced operation mode.
19. The base station according to claim 17, wherein the processor
is configured to perform the zone switch procedure using a
make-before-break method.
20. The base station according to claim 17, wherein the processor
is configured to perform the zone switch procedure using a
break-before-make method.
21. A mobile station capable of communicating in a first operation
mode and a second operation mode, comprising: one or more antennas;
a transceiver coupled to the one or more antennas for receiving and
transmitting communication data from and to base stations; and a
processor configured to: operate the first operation mode for
communicating with a first zone of a base station; establish a
communication link with the base station using the first operation
mode; determine whether the base station is capable of operating
using both the first operation mode and the second operation mode;
perform, if the base station is determined to be capable of
operating in both the first and second operation modes, a zone
switch procedure to switch the mobile station from the first zone
using the first operation mode to a second zone using the second
operation mode; and operate the second operation mode for
communicating with the second zone of the base station.
22. The mobile station according to claim 21, wherein the first
operation mode is one of a legacy operation mode and an advanced
operation mode; and the second operation mode is the other one of
the legacy operation mode and the advanced operation mode.
23. The mobile station according to claim 22, wherein the processor
is configured to determine whether the base station is capable of
operating in both the first operation mode and the second operation
mode based on a zone indicator from the base station.
24. The mobile station according to claim 21, wherein the processor
is configured to perform the zone switch procedure using a
make-before-break method.
25. The mobile station according to claim 21, wherein the processor
is configured to perform the zone switch procedure using a
break-before-make method.
26. A mobile station for wireless communication, comprising: one or
more antennas; a transceiver coupled to the one or more antennas
for receiving and transmitting communication data from and to base
stations; and a processor configured to: provide a first operation
mode for communicating with a first base station capable of
operating in the first operation mode; provide a second operation
mode for communication with a second base station capable of
operating in the first operation mode in a first zone and operating
in the second operation mode in a second zone; communicate with one
of the first base station and the second base station; and perform
a handover procedure to handover between the first base station and
the second base station.
27. The mobile station according to claim 26, wherein the first
operation mode is a legacy operation mode; and the second operation
mode is an advanced operation mode.
28. The mobile station according to claim 27, wherein, to perform
the handover procedure, the processor is configured to: obtain
information about the first zone of the second base station from
the first base station; perform the handover procedure from the
first base station to the first zone of the second base station;
obtain information about the second zone of the second base station
from the first zone of the second base station; and perform a zone
switch from the first zone of the second base station to the second
zone of the second base station.
29. The mobile station according to claim 27, wherein, to perform
the handover procedure, the processor is configured to: obtain
information about the second zone of the second base station from
the first base station; and perform the handover procedure from the
first base station to the second zone of the second base
station.
30. The mobile station according to claim 27, wherein, to perform
the handover procedure, the processor is configured to: obtain
information about the first zone of the second base station from
the first base station; start the handover procedure from the first
base station to the first zone of the second base station; receive
information about the second zone of the second base station from
the first zone of the second base station before the handover
procedure is completed; and complete the handover procedure to hand
over the mobile station from the first base station to the second
zone of the second base station.
31. The mobile station according to claim 26, wherein, to perform
the handover procedure, the processor is configured to: obtain
information about the first base station from the second base
station; and perform the handover procedure from the second zone of
the second base station to the first base station.
32. The mobile station according to claim 31, wherein, to perform
the handover procedure, the processor is further configured to:
perform a zone switch from the second zone of the second base
station to the first zone of the second base station.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from U.S. Provisional Application No. 61/096,754 to
Yung-Han Chen et al. filed on Sep. 12, 2008, the entire contents of
which are incorporated herein by reference.
TECHNICAL FIELD
[0002] The present disclosure relates generally to wireless
communication systems and, more particularly, to techniques for
switching between wireless communication systems.
BACKGROUND
[0003] A mobile wireless communication network, such as a cellular
network, is often divided into a plurality of geographically
separated, but normally overlapping cells. Each cell is controlled
by a base station (BS) for communicating with mobile stations (MS)
within the cell. When an MS moves from one cell to another cell and
the MS is transferred from one BS to another BS, a handover process
is performed by the BSs and the MS. Because the BSs may be
controlled by different network operators, these BSs may use
different communication formats, such as time division multiple
access (TDMA), frequency division multiple access (FDMA), or code
division multiple access (CDMA), The MSs may be transferred by
using different procedures, such as where the handover is initiated
by an MS or a BS.
[0004] Various techniques have been developed to perform the
handover process. For example, U.S. Pat. No. 6,115,608 issued to
Duran et al. on Sep. 5, 2000 (the '608 patent), describes an
intersystem handover method and apparatus. In the '608 patent, an
MS is aware of all the IDs of all the BSs of a different
communication system with which it is to interact and, thus,
internally initiates handoff requests. The MS monitors signals of
formats of the BSs involved for maintaining a table of received
signals from nearby cells, the cell IDs and signal quality, while
maintaining an active call and further transmits a handover request
in a command channel while in an active call mode. As another
example, U.S. Pat. No. 7,010,300 issued to Jones et al. on Mar. 7,
2006 (the '300 patent) describes a method and system for
intersystem wireless communications session hand-off. In the '300
patent, an MS uses one protocol to communicate with one access
system and uses a second protocol that encapsulates the first
protocol to communicate with a second access system. After the MS
registers with the second access system, the ongoing communication
session is handed over to the second access system according to the
second protocol over the first protocol (hand-off/switch
indication) between the MS and the first access system.
[0005] However, these conventional techniques do not address
situations in which newly developed advanced BSs co-exist with
legacy BSs. It may be desirable for the advanced BSs and MSs to
achieve backward compatibility to support the legacy BSs. Further,
if the advanced BSs and MSs support a legacy operation mode in
addition to an advanced operation mode to provide the legacy
support, a system switch procedure may be needed to transfer an
active communication session or access link between an advanced BS
and an advanced MS from the legacy operation mode to the advanced
operation mode.
[0006] Methods and systems consistent with certain features of the
disclosed embodiments address one or more of the problems set forth
above.
SUMMARY
[0007] An example in accordance with the present disclosure
includes a method of a base station for wireless communication. The
method includes providing a first zone and a second zone for
wireless communication; operating the first zone using a first
operation mode; and operating the second zone using a second
operation mode. The method also includes communicating with a
mobile station in the first zone using the first operation mode;
and determining whether the mobile station is capable of operating
using both the first operation mode and the second operation mode.
Further, the method includes performing a zone switch procedure to
switch the mobile station from the first zone using the first
operation mode to the second zone using the second operation mode,
if the mobile station is determined to be capable of operating
using both the first and second operating modes.
[0008] Another example in accordance with the present disclosure
includes a method of a mobile station capable of communicating in a
first operation mode and a second operation mode. The method
includes operating in the first operation mode for communicating
with a first zone of a base station, and establishing a
communication link with the base station using the first operation
mode. The method also includes determining that the base station is
capable of operating in both the first operation mode and the
second operation mode. Further, the method includes performing a
zone switch procedure to switch the mobile station from the first
zone using the first operation mode to a second zone using the
second operation mode and operating in the second operation mode
for communicating with the second zone of the base station.
[0009] Another example in accordance with the present disclosure
includes a method of a communication network for wireless
communication. The method includes providing a first base station
capable of operating in a first operation mode; providing a second
base station capable of providing one or more zones and operating
in at least a second operation mode; and providing at least one
mobile station capable of operating in the first operation mode and
the second operation mode. The method also includes communicating,
by the mobile station, with one of the first base station and the
second base station, and performing a handover procedure to hand
over the mobile station between the first base station and the
second base station.
[0010] Another example in accordance with the present disclosure
includes a base station for wireless communication. The base
station includes one or more antennas and a transceiver coupled to
the one or more antennas for receiving and transmitting
communication data from and to mobile stations. The base station
also includes a processor. The processor is configured to provide a
first zone and a second zone for wireless communication; to operate
the first zone using a first operation mode; and to operate the
second zone using a second operation mode. The processor is also
configured to communicate with a mobile station in the first zone
using the first operation mode; and to determine whether the mobile
station is capable of operating using both the first operation mode
and the second operation mode. Further, the processor is configured
to perform a zone switch procedure to switch the mobile station
from the first zone using the first operation mode to the second
zone using the second operation mode, if the mobile station is
determined to be capable of operating using both the first
operation mode and the second operation mode.
[0011] Another example in accordance with the present disclosure
includes a mobile station capable of communicating in a first
operation mode and a second operation mode. The mobile station
includes one or more antennas and a transceiver coupled to the one
or more antennas for receiving and transmitting communication data
from and to base stations. The mobile station also includes a
processor. The processor is configured to operate the first
operation mode for communicating with a first zone of a base
station; and to establish a communication link with the base
station using the first operation mode. The processor is also
configured to determine whether the base station is capable of
operating in both the first operation mode and the second operation
mode, and to perform a zone switch procedure to switch the mobile
station from the first zone using the first operation mode to the
second zone using the second operation mode, if the base station is
determined to be capable of operating using both the first and
second operation modes. Further, the processor is configured to
operate the second operation mode for communicating with the second
zone of the base station.
[0012] Another example in accordance with the present disclosure
includes a mobile station for wireless communication. The mobile
station includes one or more antennas and a transceiver coupled to
the one or more antennas for receiving and transmitting
communication data from and to base stations. The mobile station
also includes a processor. The processor is configured to provide a
first operation mode for communicating with a first base station
capable of operating in the first operation mode, and to provide a
second operation mode for communicating with a second base station
capable of operating in the first operation mode in a first zone
and operating in the second operation mode in a second zone. The
processor is also configured to communicate with one of the first
base station and the second base station, and to perform a handover
procedure to hand over between the first base station and the
second base station.
[0013] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory only and are not restrictive of the invention, as
claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 shows an exemplary communication environment
incorporating features consistent with disclosed embodiments;
[0015] FIG. 2 shows an exemplary BS in communication with an MS
consistent with disclosed embodiments;
[0016] FIG. 3 shows an exemplary controller consistent with
disclosed embodiments;
[0017] FIG. 4 illustrates an exemplary MS initiated zone switch
process consistent with disclosed embodiments;
[0018] FIG. 5 illustrates another exemplary MS initiated zone
switch process consistent with disclosed embodiments;
[0019] FIG. 6 illustrates an exemplary BS initiated zone switch
process consistent with disclosed embodiments;
[0020] FIG. 7 illustrates another exemplary BS initiated zone
switch process consistent with disclosed embodiments;
[0021] FIG. 8 illustrates an exemplary one-stage handover procedure
from a serving legacy BS to a target advanced BS consistent with
disclosed embodiments;
[0022] FIG. 9 illustrates an exemplary one-stage handover procedure
from a serving advanced BS to a target legacy BS consistent with
disclosed embodiments;
[0023] FIG. 10A illustrates a high-level exemplary two-stage
handover procedure from a serving legacy BS to a target advanced BS
consistent with disclosed embodiments;
[0024] FIG. 10B illustrates a high-level exemplary two-stage
handover procedure from a serving advanced BS to a target legacy BS
consistent with disclosed embodiments;
[0025] FIG. 11 illustrates an exemplary two-stage handover
procedure in detail from a serving legacy BS to a target advanced
BS consistent with disclosed embodiments;
[0026] FIG. 12 illustrates an exemplary two-stage handover
procedure in detail from a serving legacy BS to a target advanced
BS consistent with disclosed embodiments; and
[0027] FIG. 13 illustrates an exemplary process performed by an MS
for target network entry consistent with disclosed embodiments.
DETAILED DESCRIPTION
[0028] Reference will now be made in detail to embodiments of the
invention, examples of which are illustrated in the accompanying
drawings. Wherever possible, the same reference numbers will be
used throughout the drawings to refer to the same or like
parts.
[0029] FIG. 1 shows an exemplary communication environment 100
incorporating features consistent with embodiments of the present
invention. As shown in FIG. 1, communication environment 100, such
as a wireless communication network using various systems, e.g.,
code division multiple access (CDMA), wideband code division
multiple access (WCDMA), wireless local area network (WLAN),
worldwide interoperability for microwave access (WiMAX), and OFDM,
may include a base station (BS) 110, a BS 120, and a mobile station
(MS) 130. The number of BSs and MSs is exemplary only and not
intended to be limiting. Any number of BSs and MSs may be used, and
other devices may be added. BS 110 may control a cell 112, and
BS120 may control a cell 122. MS 130 may move between locations
controlled by different BSs. For example, as shown in FIG. 1, MS
130 may move from one location controlled by BS 110 to another
location controlled by BS 120, and overlapped with BS 110.
[0030] Further, BS 110 may be an advanced BS and BS 120 may be a
legacy BS. Other types of systems, however, may also be used. A
legacy BS, as used herein, may refer to a base station that
operates in a legacy operation mode according to legacy
specifications. A legacy specification is used relative to an
advance specification. A legacy specification may refer to a
specification of a standard, such as IEEE 802.16, that is still in
use but is outdated by another specification of the standard,
usually providing improvement on speed, bandwidth, and/or
efficiency (i.e., an advanced specification). An advanced BS, as
used herein, may refer to a base station that operates in an
advanced operation mode according to one or more advanced
specifications. The advanced BS may also support the legacy
operation mode in order to be backward compatible with the legacy
BS.
[0031] For example, a BS according to IEEE 802.16e standards, which
has been included in IEEE 802.16Rev2, may be considered as a legacy
BS; while a BS according to IEEE 802.16m standards may be
considered as an advanced BS, which may provide backward
compatibility with the IEEE 802.16e standards. Other standards,
however, may also apply.
[0032] Advanced BS 110 may include two or more different zones,
e.g., a legacy zone and an advanced zone. A zone, as used herein,
may refer to a set of systems, hardware resources, and/or software
resources configured by a BS to support a particular operation mode
within a cell. For example, a zone may include a block or segment
of time and/or frequency resources for the particular operation
mode. A legacy zone thus may mean a time duration and/or a
frequency band that is dedicated for legacy communications and
operations and an advanced zone may mean a time duration and/or a
frequency band that is dedicated for advanced communications and
operations. Further, a zone may also include a certain coverage
area within the cell. Any appropriate time/space/frequency
resources may be included in a zone.
[0033] In operation, BS 110 may reserve resources for access with
the legacy operation mode for the legacy zone, and may also reserve
resources for access with the advanced operation mode for the
advanced zone. The coverage of the legacy zone and the advanced
zone may cover different areas within cell 112; may overlap certain
areas within cell 112; or may coincide with each other. The
resources may include any appropriate hardware and/or software
resources used in wireless communication, such as memory,
processor, backend server, network operation equipment, databases,
transmission opportunities, etc.
[0034] MS 130 may also operate in both an advanced operation mode
and a legacy operation mode. Thus, MS 130 may choose a particular
operation mode to access BS 110. For example, MS 130 may use the
legacy operation mode to access a legacy zone of BS 110; or may use
the advance operation mode to access an advanced zone of BS 110.
Further, MS 130 may switch the access between the legacy zone and
the advanced zone by using zone switch procedures or system switch
procedures.
[0035] A zone that currently serves MS 130 or provides an active
access link may be referred to as a serving zone, and a zone that
MS 130 switches to may be referred to as a target zone. Thus, the
legacy zone and the advanced zone of BS 110 may be either the
serving zone or the target zone, and the zone switch may be from
the legacy zone to the advanced zone or from the advanced zone to
the legacy zone. Further, the zone switch procedures may be
initiated by either MS 130 or BS 110.
[0036] During the zone switch, MS 130 may perform a target zone
entry procedure to establish an access link with a target zone. If
MS 130 terminates the access link with a serving zone before
performing the target zone entry procedure, it is called a
break-before-make zone switch because MS 130 breaks the original
access link before making the target zone entry. A
break-before-make zone switch may also be called a
break-before-entry zone switch.
[0037] On the other hand, if MS 130 terminates the access link with
the serving zone after performing the target zone entry procedure,
it is called a make-before-break zone switch because MS 130 makes
the target zone entry before it breaks the original link. A
make-before-break zone switch may also be called an
entry-before-break zone switch.
[0038] Again with reference to FIG. 1, BS 110 and BS 120 may
include any appropriate type of wireless or radio base station,
such as a land-based communication base station or a
satellite-based communication base station, according to certain
standards, such as IEEE 802.16e, IEEE 802.16m, or other standards.
FIG. 2 shows an exemplary BS 210 representing BS 110 or BS 120 in
communication with MS 130.
[0039] As shown in FIG. 2, BS 210 may include any appropriate type
of voice, data, and/or integrated voice and data communication
equipment to provide high speed data and/or voice communications.
For example, BS 210 may include a transceiver 220 and one or more
antennas 240. Transceiver 220 may include any appropriate type of
transmitter and receiver to transmit data from BS 210 to other
wireless devices and to receive data from the other wireless
devices. Transceiver 220 may include any desired functional
component(s), processor(s), and/or circuitries to provide
coding/encoding, modulation/demodulation, pilot symbol
insertion/removal, and other wireless channel related functions.
Further, transceiver 220 may use one or more antennas 240 for
transmitting and receiving in different configurations, such as
single-input and single-output (SISO), single-input and
multiple-output (SIMO), multiple-input and single-output (MISO),
and multiple-input and multiple-output (MIMO).
[0040] MS 130 may include any appropriate communication terminal
capable of communicating with BS 210 based on any of the various
communication standards, such as IEEE 802.16 standards (e.g., IEEE
802.16e, IEEE 802.16m), IEEE 802.11 standards, CDMA, WCDMA, GSM,
etc. MS may include terminal devices such as a mobile phone, a
hand-held device, or any type of wireless device. MS 130 may also
be configured to communicate with other communication terminals
(not shown) directly or indirectly via BS 210, such as a landline
communication device or a wireless communication device. Further,
MS 130 may include a wireless communication transceiver 230 for
carrying out the communication between MS 130 and BS 210 and/or
between MS 130 and the other communication terminals.
[0041] Transceiver 230 may include any appropriate type of mobile
device communication transceiver, i.e., a combination of a
transmitter and a receiver having a common frequency control.
Transceiver 230 may include various circuitries provided for
processing signals generated during the transmitting and/or
receiving operations of transceiver 230.
[0042] Further, MS 130 may include one or more antennas 250 used by
transceiver 230 to receive and transmit signals from and to BS 210.
MS 130 may also be configured to operate in SISO, SIMO, MISO,
and/or MIMO mode. MS 130 receives signals or data from BS 210
through a downlink (DL) channel established between MS 130 and BS
210 and transmits signals or data to BS 210 through an uplink (UL)
channel established between MS 130 and BS 210.
[0043] Operations of MS 130 and/or BS 210 may be controlled by a
controller (not shown in FIG. 2). FIG. 3 shows an exemplary
controller 300 that may be implemented in MS 130 and/or BS 210. As
shown in FIG. 3, controller 300 may include a processor 302, a
random access memory (RAM) 304, a read-only memory (ROM) 306, a
storage 308, an input/output interface 310, and a communication
interface 312. It is understood that the type and number of devices
included in controller 300 are exemplary only and not intended to
be limiting. The number of listed devices may be changed, certain
devices may be removed, and other devices may be added.
[0044] Processor 302 may include any appropriate type of general
purpose microprocessor, digital signal processor, application
specific integrated circuit (ASIC), and/or microcontroller.
Processor 302 may execute sequences of computer program
instructions to perform various information processing functions
and control functions. Processor 302 may be coupled to or access
other devices, such as transceivers, other processors, radio
frequency (RF) devices, and/or antennas.
[0045] RAM 304 and ROM 306 may include any appropriate type of
random access memory, read only memory, or flash memory. Storage
308 may include any appropriate type of mass storage provided to
store any type of information that processor 302 may need to
perform processing/functions. For example, storage 308 may include
one or more hard disk devices, optical disk devices, floppy disk
devices, and/or other storage devices to provide storage space.
[0046] Input/output interface 310 may send control and data signals
to other devices from processor 302 and may receive control and
data signals sent from other devices to processor 302.
Communication interface 312 may provide communication connections
to enable controller 300 to exchange information with other systems
via, for example, computer networks, such as the Internet.
[0047] As explained previously, a zone switch may be performed
between MS 130 and BS 110, and the zone switch may be initiated by
either MS 130 or BS 110. FIG. 4 illustrates an exemplary MS
initiated zone switch process. Unless otherwise stated, all steps
in the processes disclosed in this application are performed by BS
110, BS 120, and/or MS 130 and, more particularly, by processor 302
of BS 110, BS 120, and/or MS 130.
[0048] As shown in FIG. 4, the zone switch may be initiated by MS
130 via a make-before-break zone switch procedure with BS 110,
which is an advanced BS. At the beginning, MS 130 identifies BS
110's capability of performing zone switch (402). BS 110 is capable
of performing zone switch if BS 110 can activate both a legacy zone
and an advanced zone for communication with MS 130. There may be
several ways for BS 110 to announce the capability of performing
zone switch to MS 130. For example, BS 110 may announce the
capability using a type of indication message, e.g., alternative
zone indication (ALT_ZON-IND) message to MS 130, or BS 110 may
announce the capability using an alternative zone indicator carried
by other types of messages to MS 130.
[0049] The alternative zone indicator may be a flag, a bit, or
several bits in the messages. For example, a reserved bit in the
frame control header (FCH) of IEEE 802.16 systems may be used to
represent the alternative zone indicator, as shown in Table 1
below.
TABLE-US-00001 TABLE 1 Alternative zone indicator by FCH
modification Syntax Size (bit) Notes DL_Frame_Prefix_Format( ) {
Used subchannel bitmap 6 Bit #0: Subchannel group 0 Bit #1:
Subchannel group 1 Bit #2: Subchannel group 2 Bit #3: Subchannel
group 3 Bit #4: Subchannel group 4 Bit #5: Subchannel group 5
Alternative Zone Indicator 1 0: Do not support 16m access 1:
Support 16m access Repetition_Coding_Indication 2 0b00: No
repetition coding on DL-MAP 0b01: Repetition coding of 2 used on
DL-MAP 0b10: Repetition coding of 4 used on DL-MAP 0b11: Repetition
coding of 6 used on DL-MAP Coding_Indication 3 0b000: CC encoding
used on DL-MAP 0b001: BTC encoding used on DL-MAP 0b010: CTC
encoding used on DL-MAP 0b011: ZT CC encoding used on DL-MAP 0b100:
CC encoding with optional interleaver 0b101: LDPC encoding used on
DL-MAP 0b110 to 0b111: Reserved DL-Map_Length 8 Reserved 4 Shall be
set to zero }
[0050] As shown in Table 1, the alternative zone indicator includes
a single reserved bit. The single reserved bit having a value of
`1` indicates the capability of zone switch (e.g., advanced
operation mode according to IEEE 802.16m); while having a value of
`0` indicates no support for zone switch. Other methods of
detecting the capability of zone switch may also be used.
[0051] After identifying that BS 110 is capable of performing zone
switch (402), MS 130 sends a zone switch request message, such as
an MSZS-REQ (MS zone switch request) message to BS 110 (404). MS
130 sends the MSZS-REQ to BS 110 through the serving zone to ask
for performing zone switch. The zone switch request contains
identification of MS 130 to inform BS 110 who is asking for the
zone switch.
[0052] After receiving the zone switch request from MS 130, BS 110
determines whether to accept or reject the zone switch request. If
BS 110 determines to accept the zone switch request, BS 110
performs zone switch preparation (406). For example, BS 110 may
check if the target zone is activated or not. If the target zone is
not activated, BS 110 activates the target zone during zone switch
preparation. BS 110 may also allocate resources in target zone to
support the same quality of service (QOS) in the serving zone.
Further, BS 110 may transfer or map the user profile and all
parameters, messages, and resource for link control such as
authentication, key management, registration information, timers,
buffers, retransmission sequences, and other required entities from
the serving zone to the target zone.
[0053] BS 110 also replies to MS 130 with a zone switch response
(MSZS-RSP) message (408). The MSZS-RSP message may include
information related to the zone switch, including target zone
information, such as the synchronization parameters (e.g.,
synchronization channel index, timing offset for the target zone),
new MS identification, a zone switch timer, and optional new
security configuration/parameters.
[0054] On the other hand, if BS 110 rejects the zone switch
request, BS 110 may ignore the request or send a MSZS-RSP message
with reject indication to MS 130. If MS 130 does not receive the
zone switch response within a period of time or receives the reject
indication, MS 130 stops the zone switch procedure.
[0055] Assuming BS 110 accepts the zone switch request and
indicates such acceptance in the MSZS-RSP message, MS 130 turns on
operation mode for the target zone (410). MS 130 also performs a
target zone entry procedure to establish an access link with the
target zone (412). If target zone entry procedure is successfully
completed before the zone switch timer expires, MS 130 sends a zone
switch indication message, such as an MSZS-IND (MS zone switch
indication) message to BS 110 through the serving zone to notify BS
110 that the target zone entry procedure is successful (414).
[0056] After receiving the MSZS-IND message, BS 110 releases
serving zone resources for MS 130 and clears serving zone state
machine parameters for MS 130 (416). BS 110 also confirms the
success of target zone entry and the resource release in the
serving zone. MS 130 turns off the operation mode for the serving
zone (418).
[0057] FIG. 5 illustrates another exemplary MS initiated zone
switch process. As shown in FIG. 5, the zone switch may be
initiated by MS 130 via a break-before-make zone switch procedure
with BS 110. Operations 502, 504, 506, and 508 are the same as
operations 402, 404, 406, and 408, illustrated in FIG. 4,
respectively.
[0058] In 510, MS 130 sends a zone switch indication message, such
as an MSZS-IND (MS zone switch indication) message to BS 110 before
performing any target zone entry procedure. After receiving the
MSZS-IND message, BS 110 releases serving zone resources for MS 130
(512), which is similar to 416 (FIG. 4). BS 110 receives the
MSZS-IND message through the serving zone.
[0059] Further, MS 130 turns on the operation mode for the target
zone and turn off the operation mode for the serving zone (514),
similar to 410 and 418 (FIG. 4). Further, MS 130 performs a target
zone entry procedure to establish an access link with the target
zone (step 516), similar to 412 (FIG. 4).
[0060] For the above zone switch processes shown in FIGS. 4 and 5,
if MS 130 wants to cancel the zone switch procedure, MS 130 may use
the zone switch indication message to send a cancellation request
to BS 110 through the serving zone. After receiving the
cancellation request, BS 110 stops the zone switch procedure and
does not release the resources for MS 130 in the serving zone.
Further, MS 130 may also determine whether to use the
make-before-break method or the break-before-make method based upon
certain conditions, such as the current status of the serving zone
and target zone, the estimated success rate of the zone switch, and
status and quality of current access link with BS 110, etc.
[0061] FIG. 6 illustrates an exemplary BS initiated zone switch
process. As shown in FIG. 6, the zone switch may be initiated by BS
110 via a make-before-break zone switch procedure with MS 130. At
the beginning, BS 110 identifies MS 130's capability of performing
zone switch (602). MS 130 is capable of performing zone switch if
MS 130 can support both a legacy operation mode and an advanced
operation mode for communication with BS 110. There may be several
ways for BS 110 to identify the capability of performing zone
switch of MS 130.
[0062] For example, BS 110 may be able to detect an advanced MS
indication message or an advanced MS indicator carried in other
messages from MS 130. MS 130 may send the advanced MS indication
message or an advanced MS indicator carried in other messages upon
a request from BS 110 or voluntarily. The advanced MS indication
message or an advanced MS indicator may indicate whether MS 130 is
an advanced MS or a legacy MS.
[0063] The advanced MS indicator may be a flag, a bit, or several
bits in certain types of messages. For example, the advanced MS
indicator may be carried by the uplink control message such as a
reserved bit in the ranging request (RNG-REQ) in IEEE 802.16 based
systems, as shown in Table 2 below.
TABLE-US-00002 TABLE 2 Advanced MS indicator by RNG-REG
modification Syntax Size (bit) Notes RNG-REQ_Message_Format( ) {
Management Message Type = 4 8 -- Advanced MS Indicator 1 0: Legacy
MS 1: Advanced MS Reserved 7 Shall be set to zero TLV Encoded
Information variable TLV-specific }
[0064] As shown in Table 2, the advanced MS indicator may include a
single reserved bit. The single reserved bit having a value of `1`
indicates capability of zone switch (e.g., advanced mode according
to IEEE 802.16m); while having a value of `0` indicates no support
for zone switch.
[0065] After identifying that MS 130 has the capability to perform
the zone switch (602), BS 110 performs zone switch preparation
(step 604). For example, BS 110 may check if the target zone is
activated or not. If the target zone is not activated, BS 110 may
activate the target zone during zone switch preparation. BS 110 may
also allocate resources in target zone to support the same quality
of service (QOS) in the serving zone. Further, BS 110 may transfer
or map the user profile and all parameters, messages, and resources
for link control such as authentication, key management,
registration information, timers, buffers, retransmission
sequences, and other required entities from the serving zone to the
target zone.
[0066] Further, BS 110 sends MS 130 a zone switch request message
(e.g. BSZS-REG) to initiate the zone switch procedure. The zone
switch request message may contain target zone information, such as
the synchronization parameters (e.g., synchronization channel
index, timing offset for the target zone), new MS identification, a
zone switch timer, and optional new security
configuration/parameters. Other information may also be included in
the zone switch request message.
[0067] The remaining operations 608, 610, 612, 614, and 616 are
similar to operations 410, 412, 414, 416, and 418, illustrated in
FIG. 4, respectively, to complete the zone switch procedure between
MS 130 and BS 110 via a make-before-break procedure.
[0068] FIG. 7 illustrates another exemplary BS initiated zone
switch process. As shown in FIG. 7, the zone switch may be
initiated by BS 110 via a break-before-make zone switch procedure
with MS 130. Operations 702, 704, and 706 are the same as
operations 602, 604, and 606, illustrated in FIG. 6, respectively.
Further, operations 708, 710, 712, and 714 are the same as or
similar to operations 510, 512, 514, and 516, illustrated in FIG.
5, respectively, for completing the zone switch procedure between
MS 130 and BS 110 via a break-before-make procedure.
[0069] Similar to the MS initiated zone switch procedure, during
the BS initiated zone switch procedure shown in FIGS. 6 and 7, if
MS 130 wants to cancel the zone switch procedure, MS 130 may use
the zone switch indication message to send a cancellation request
to BS 110 through the serving zone. After receiving the
cancellation request, BS 110 stops the zone switch procedure and
keeps the resource for MS 130 in the legacy zone.
[0070] Returning to FIG. 1, MS 130 may move from cell 112 to cell
122 or move from cell 122 to cell 112, and handover procedures may
be performed such that MS 130 maintains active communication
sessions or links when switching between BSs respectively
corresponding to the cells. The BS controlling the cell to which MS
130 switches may be referred to as a target BS, and the BS
controlling the cell from which MS 130 switches may be referred to
as a serving BS. The serving BS or the target BS can be either an
advanced BS or a legacy BS. Thus, the handover procedures may
include handover procedures from a serving legacy BS to a target
advanced BS and from a serving advanced BS to a target legacy BS.
The handover procedures between the same systems, i.e., from a
serving legacy BS to a target legacy BS and from a serving advanced
BS to a target advanced BS are within systems of the same standards
and are not discussed herein in detail.
[0071] Further, the handover procedures may include a one-stage
handover procedure and a two-stage handover procedure. A one-stage
handover, as used herein, refers to a single switchover from the
serving BS to the target BS; while a two-stage handover refers to
more than a single switchover from the serving BS to the target BS.
For example, a two-stage handover may include a switchover from the
serving BS to the target BS and a zone switch from a serving zone
to a target zone. FIG. 8 illustrates an exemplary one-stage
handover procedure from a serving legacy BS (e.g., BS 120) to a
target advanced BS (e.g., BS 110).
[0072] As shown in FIG. 8, MS 130 obtains neighbor cell information
(802). MS 130 may obtain the neighbor cell information from the
serving legacy BS (BS 120). For example, MS 130 may receive and
analyze certain messages from the serving BS and/or from the target
BS to obtain neighbor cell information. MS 130 analyzes the
neighbor cell information based on a relationship between legacy
synchronization information and advanced synchronization
information. That is, the serving legacy BS (BS 120) includes a set
of legacy synchronization information to indicate or imply to MS
130 that some neighbor BS may be advanced BSs.
[0073] For example, legacy BS 120 using IEEE 802.16e standards may
add a legacy preamble index into neighbor cell advertisement
messages (e.g., MOB_NBR-ADV) to imply the existence of neighbor
advanced BSs using IEEE 802.16m standards. That is, MS 130 may scan
and search neighboring legacy BSs based on the legacy
synchronization information in the neighbor cell advertisement
messages, and may scan and search neighboring advanced BSs based on
information mapping from the legacy synchronization information in
the neighbor cell advertisement messages.
[0074] The legacy neighbor cell advertisement messages may
implicitly or explicitly contain the information about neighboring
advanced BSs, such as the synchronization information and the
capability information. Also, mapping relationships between legacy
preambles (e.g., IEEE 802.16e) and advanced preambles (e.g., IEEE
802.16m) may be pre-defined. Thus, a legacy BS (e.g., IEEE 802.16e)
may add an advanced (e.g., IEEE 802.16e) preamble index into the
MOB_NBR-ADV messages to imply possible preambles of the neighboring
advanced (e.g., IEEE 802.16m) BSs. MS 130, with a legacy serving BS
(BS 120), may scan neighboring legacy BSs based on the legacy
(e.g., IEEE 802.16e) preamble index recommended in the MOB_NBR-ADV
messages, and may also scan neighboring advanced BSs based on the
preambles related to the advanced (e.g., IEEE 802.16e) preamble
index.
[0075] For example, information about neighbor BSs may be inserted
into a legacy neighbor cell advertisement message (e.g.
MOB_NBR-ADV). The format of inserted advanced BS information should
be compatible with the legacy format, so the information may need
to be re-defined. Further, an indicator may be added to specify
that the neighbor information is from a legacy BS or an advanced
BS. For example, the `Preamble Index` field in an IEEE 802.16e
MOB_NBR-ADV message is an 8-bit field, in which the most
significant bit (MSB) is a reuse factor, and the remaining 7 bits
represent 114 preamble indexes. Because there are at least 512
secondary synchronization channels (S-SCH), or called secondary
advanced preamble according to IEEE 802.16m, the `Preamble Index`
field may be unable to represent all the S-SCHs in the IEEE 802.16e
MOB_NBR-ADV message.
[0076] However, because the field `Preamble Index` in the
MOB_NBR-ADV message can represent 128 values (7 bits), and only 114
values are used, 14 values are unused. Further, if counting in the
MSB, which is the reuse factor of 2, a total 28 values are unused.
Thus, these 28 unused values may be used as a demarcation between
IEEE 802.16e preamble/SCH indexes and IEEE 802.16m information. It
may be assumed that the values 0 to 113 are assigned to represent
the IEEE 802.16e preamble indexes in the IEEE 802.16e preamble
index set. In other words, if the value of the `Preamble Index`
field is smaller than or equal to 113 (belongs to 16e preamble
index set), all IEEE 802.16e and IEEE 802.16m systems recognize the
value as a valid IEEE 802.16e preamble index. However, if the value
of `Preamble Index` field is greater than 113, an IEEE 802.16e
system may skip this neighbor information because it cannot
recognize it, while an IEEE 802.16m system may recognize the value
as valid IEEE 802.16m neighbor information. Further, the IEEE
802.16m neighbor information may be encoded according to a legacy
TLV (type, length, and value) principle with predefined parameters
and entities.
[0077] After obtaining neighbor cell information (802), MS 130 may
find candidate neighboring advanced base stations based on the
neighbor cell information (804). Alternatively or additionally, MS
130 may also discover new target BSs by using autonomous base
stations scanning. Further, MS 130 may determine a target advanced
BS (e.g., BS 110) based on predetermined criteria, such as signal
quality or communication quality, etc. Further, MS 130 or serving
BS 120 may initiate legacy handover procedures with the serving
legacy BS (806). After legacy handover procedures are finished, MS
130 or serving BS 120 may terminate the access link with the
serving legacy BS (806).
[0078] Further, MS 130 may turn on an advance operation mode (808),
and may perform advanced network entry procedures with the target
advanced BS (810) and perform advance network entry procedures
through the advanced zone of the target advanced BS. After
completing the advanced network entry procedures (810), MS 130 and
the target advanced BS (e.g., BS 110) can enter normal operation in
advanced operation mode (812).
[0079] FIG. 9 illustrates an exemplary one-stage handover procedure
from a serving advanced BS (BS 110) to a target legacy BS (BS 120).
As shown in FIG. 9, MS 130 may obtain neighbor cell information
(902). MS 130 may obtain the neighbor cell information from the
serving advanced BS (BS 110). For example, MS 130 may receive and
analyze certain messages from the serving BS and/or from the target
BS to obtain neighbor cell information.
[0080] The serving advanced BS (BS 110) may be able to provide
neighbor base station synchronization information for both legacy
and advanced BSs. For example, BS 110 may broadcast the neighbor
cell advertisement messages to include the synchronization
information of the neighboring legacy (e.g., IEEE 802.16e) and
advanced (e.g., IEEE 802.16m) BSs. Using this information, MS 130
may be able to perform neighbor BS scanning for both neighboring
legacy BSs and advanced BSs.
[0081] After obtaining neighbor cell information (902), MS 130 may
perform base station scanning based on the neighbor cell
information to find candidate neighboring legacy base stations
(904). Alternatively or additionally, MS 130 may also discover new
target BSs by using autonomous base station scanning. Further, MS
130 may find candidate neighboring BSs and identify a target legacy
BS (e.g., BS 120) based upon predetermined criteria, such as signal
quality or communication quality, etc. MS 130 or serving BS 110 may
also initiate advanced handover procedures (906). After the
advanced handover procedures are completed, MS 130 or serving BS
110 may terminate the access link between MS 130 and the serving
advanced BS 110 (906).
[0082] Further, MS 130 turns on legacy operation mode (908), and
performs legacy network entry procedures with the target legacy BS
(910). After completing the legacy network entry procedures (910),
MS 130 and the target legacy BS (e.g., BS 120) enter the normal
operation in legacy operation mode (912).
[0083] FIG. 10A illustrates a high-level exemplary two-stage
handover procedure from a serving legacy BS to a target advanced
BS. As shown in FIG. 10A, MS 130 performs a legacy handover and
network entry procedures in stage 1 (1002). That is, MS 130,
serving legacy BS 120, and target advanced BS 110 complete the
legacy handover procedures, such as the neighbor BS scanning, the
handover process, network entry procedures, etc., such that MS 130
is handed over from serving legacy BS 120 to a target advanced BS
110's legacy zone.
[0084] Further, MS 130 and advanced BS 110 perform the zone switch
procedures to switch the access link between MS 130 and BS 110 from
the legacy zone to the advanced zone in stage 2 (1004). The zone
switch procedures may be initiated by MS 130 or target advanced BS
110, using the make-before-break or the break-before-make method,
as described in previous sections. After the zone switch
procedures, MS 130 and advanced BS 110 perform normal operation in
the advanced operation mode (1006).
[0085] FIG. 10B illustrates a high-level exemplary two-stage
handover procedure from a serving advanced BS (e.g., BS 110) to a
target legacy BS (e.g., BS 120). As shown in FIG. 10B, MS 130 and
serving advanced BS 110 perform the zone switch procedures in stage
1 to switch the access link between MS 130 and BS 110 from advanced
zone to legacy zone (1052). The zone switch procedures may be
initiated by MS 130 or by target advanced BS 110, using the
make-before-break or the break-before-make method, as described in
previous sections.
[0086] Further, MS 130 and target legacy BS 120 may complete legacy
handover procedures (1054), such as the neighbor BS scanning, the
handover process, network entry procedures, etc., in stage 2 such
that MS 130 is handed over from serving advanced BS 110 to target
legacy BS 120. After the handover procedures, MS 130 and legacy BS
120 perform normal operation in legacy operation mode (1056).
[0087] Although FIG. 10A and FIG. 10B illustrate that stage 1 and
stage 2 are performed separately, the separation of stage 1 and
stage 2 is used for illustrative purposes only. Stage 1 and stage 2
are not completely independent procedures, and procedures for stage
1 and stage 2 may be closely integrated for various advantages such
as efficiency, speed, signaling, and/or practicality. FIG. 11
illustrates an exemplary two-stage handover procedure from a
serving legacy BS to a target advanced BS.
[0088] As shown in FIG. 11, MS 130 sends serving legacy BS 120 a
handover request via a handover request message (MOB_MSHO-REQ)
(1102). After receiving the handover request, serving legacy BS 120
performs handover preparation (1104) and sends MS 130 a handover
response via a handover response message (MOB_MSH-RSP) (1106).
Further, MS 130 sends serving legacy BS 120 a handover indication
via a handover indication message (MOB_HO-IND) (1108). After
receiving the MOB_HO-IND message from MS 130, serving legacy BS 120
performs backbone signaling to notify target advanced BS 110 about
the handover along with information about MS 130 (1110). Backbone
signaling refers to a set of actions to signal elements of backend
networks of a BS, such as a home location register (HLR), a
visiting location register (VLR), and/or an authentication,
authorization and accounting (AAA) server. Further, serving legacy
BS 120 terminates the access link between MS 130 and serving legacy
BS 120 and releases resources for MS 130 (1112).
[0089] MS 130 performs downlink synchronization with target
advanced BS 110 (step 1114) and obtains uplink parameters from
target advanced BS 110 (1116). MS 130 performs these actions in
legacy operation mode with the legacy zone of BS 110 to perform the
legacy network entry procedures to the legacy zone of target
advanced BS 110. However, when performing a ranging request
(RNG-REQ) during the legacy network entry procedures, MS 130 may
insert an advanced MS indicator in the ranging request message to
inform target advanced BS 110 that MS 130 is an advanced (e.g.,
IEEE 802.16m) MS.
[0090] After receiving the advanced MS indicator from MS 130,
target advanced BS 110 starts to perform BS-initiated zone switch
procedures from the legacy zone to the advanced zone via 1120,
1122, 1124, 1126, 1128, 1130, and 1132, which are the same as 604,
606, 608, 610, 612, 614, and 616, illustrated in FIG. 6,
respectively, to complete the zone switch. After completing both
the handover procedures and the zone switch procedure, MS 130 and
target advanced BS 110 enter normal operation in the advanced
operation mode (1134). In certain embodiments, after receiving the
advanced MS indicator from MS 130, target advanced BS 110 may
directly hand over MS 130 from the legacy zone of serving legacy BS
120 to the advanced zone of target advanced BS 110 before the
handover procedure between the legacy zone of serving legacy BS 120
to the legacy zone of target advanced BS 110 is completed.
[0091] FIG. 12 illustrates an exemplary two-stage handover
procedure from a serving legacy BS (e.g., BS 120) to a target
advanced BS (e.g., BS 110). MS 130 sends a legacy neighbor base
station scan request message (MOB_SCN-REQ) to serving legacy BS 120
(1202). Serving legacy BS 120 returns a legacy neighbor base
station scan response message (MOB_SCN-RSP) to MS 130 (1204). The
response message may include information about neighboring legacy
BSs including the legacy zone of target advanced BS 110.
[0092] Based upon the information in the response message, MS 130
synchronizes and measures neighboring legacy BSs and the legacy
zone of target advanced BS 110 (1206), and determines a handover to
the legacy zone of target advanced BS 110. Further, MS 130 sends
serving legacy BS 120 a handover request via a handover request
message (MOB_MSHO-REQ) (1208). After receiving the handover
request, serving legacy BS 120 performs handover preparation and
sends MS 130 a handover response via a handover response message
(MOB_BSHO-RSP) (1210). Further, MS 130 sends serving legacy BS 120
a handover indication via a handover indication message
(MOB_HO-IND) (1212). Serving legacy BS 120 also terminates the
access link between MS 130 and serving legacy BS 120 and releases
resources for MS 130.
[0093] MS 130 may also obtain broadcast messages from the legacy
zone of target advanced BS 110 (1212). The broadcast message may
include information about capability of target advanced BS 110,
such as FCH (frame control header) and DCD (downlink channel
description (1214)). MS 130 may perform target network entry
procedures based upon the information obtained from the legacy zone
of target advanced BS 110 (1216). FIG. 13 illustrates an exemplary
process performed by MS 130 for target network entry.
[0094] As shown in FIG. 13, MS 130 scans and reads FCH for an
advanced base station capability indicator (1302). For example, MS
may read an "IEEE 802.16m" indicator, such as the alternative zone
indicator in Table 1, and determine whether the value of the
indicator is true or `1` (step 1304). If MS 130 determines that the
value of the indicator is `1` (1304; yes), MS 130 reads DCD
extended TLV in the legacy zone message to obtain detailed advanced
(e.g., IEEE 802.16m) zone information (1306). MS 130 then performs
network entry procedures in advanced operation mode (1308). On the
other hand, if MS 130 determines that the value of the indicator is
not `1` (1304; no), MS 130 performs network entry procedures in
legacy operation mode (1310).
[0095] Returning again to FIG. 12, after performing the network
entry procedures (1216), MS 130 enters normal operation with BS 110
(1218). If MS 130 performed network entry procedures in legacy
operation mode, MS 130 enters normal operation with BS 110 in
legacy operation mode. Otherwise, MS 130 enters normal operation
with BS 110 in advanced mode.
[0096] Other embodiments of the invention will be apparent to those
skilled in the art from consideration of the specification and
practice of the invention disclosed herein. It is intended that the
specification and examples be considered as exemplary only, with a
true scope and spirit of the invention being indicated by the
following claims.
* * * * *